The arthropod-borne filarial parasite Wuchereria bancrofti is the leading cause of filariasis and elephantiasis in tropical and sub-tropical regions of the world. Epidemiological data are poor, but it is estimated that about 100 million people are infected worldwide. The disease is both physically and psychologically debilitating and appears to be increasing in prevalence in many nations. In Egypt, for example, the disease was virtually eliminated during the period 1910-1965, but seems to have increased dramatically in prevalence since that time. Detection and identification of filarial parasites in human blood samples and in mosquitoes is a difficult and time-consuming process when using traditional morphological staining/microscopy techniques. The use of cloned species- specific DNA probes to detect parasites in humans and in mosquitoes would provide a valuable tool for studying the epidemiology of this disease. Analysis of DNA isolated from W. bancrofti from Indonesia has demonstrated the existence of highly repeated genetic elements in this species. Repeat DNA has been cloned from the Indonesian parasites, and these sequences have proven to be both sensitive and species-specific in DNA dot blot hybridization assays. Studies of the rate of evolution of highly repeated DNA elements in filarial parasites has revealed that these sequences evolve very rapidly. For example, the Hha I repeat found in Brugia parasites is not found in W. bancrofti. Thus, it will be necessary to study W. Bancrofti highly repeated DNA from geographic isolates distant from Indonesia. In this study, scientists from the United States, Egypt and Israel will collaborate to clone and characterize highly repeated DNA sequences from W. bancrofti isolated in Egypt. The structure, organization and copy number of these repeats will be studied at the DNA sequence level and comparison will be made to repeats cloned from the Indonesia isolate. Experiments to determine the sensitivity and species-specificity of these sequences will be necessary to assess their potential as useful DNA probes in parasite detection assays. The next step will be the development of rapid, simple, and inexpensive non-radioactive assays to detect Egyptian W. bancrofti in human blood and in mosquitoes. Finally, these probes will need to be tested in field studies conducted in endemic regions of Egypt.